Field of the Invention
The present disclosure relates to a toner for developing an electrophotograph and an electrostatic image (electrostatic latent image) to be used in an image forming method, such as an electrostatic printing method.
Description of the Related Art
In recent years, along with the development of computers or multimedia, environments in which an electrophotography type image forming method is used have diversified, and there is a need to output stable images for a long time even under severe environments such as a low temperature and low humidity environment or a high temperature and high humidity environment. To this end, a toner is required to exhibit stable chargeability even though it is used over a long period of time, and studies for improving durability and chargeability of the toner has been widely conducted.
In Japanese Patent Application Laid-Open No. 2016-021041, there is a disclosure of a toner having a condensate of an organosilicon compound having a specific structure in its surface layer in order to improve development durability and environmental stability of charging.
In Japanese Patent Application Laid-Open No. H08-184988, there is a disclosure of a toner in which alumina fine particles surface-treated with an organosilicon compound are externally added for suppressing overcharge in a low temperature and low humidity environment.
In Japanese Patent Application Laid-Open No. 2015-219388, there is a disclosure of a toner which has a surface layer made of a thermosetting resin such as a melamine resin, and of which a charge attenuation constant is controlled in order to suppress overcharge.
In Japanese Patent Application Laid-Open No. H08-292599, there is a disclosure of a toner in which a surface of a toner to which inorganic particles are fixed is coated with a silane coupling agent.
Since the toner disclosed in Japanese Patent Application Laid-Open No. 2016-021041 has a condensate of the organosilicon compound having high strength and high chargeability, the toner may have excellent development durability even in a low temperature and low humidity environment or a high temperature and high humidity environment. Further, the toner stably has high chargeability. However, since the condensate of the organosilicon compound has high resistance, in some cases, the toner may be over-charged in the lower temperature and low humidity environment. Overcharging of the toner sometimes causes adverse effects such as adhesion of the toner to a developing member or a carrier, such that there is room for improvement.
As a method of suppressing a toner from being over-charged, a method of adding the alumina fine particle surface-treated with the organosilicon compound from the outside to a toner has been suggested in Japanese Patent Application Laid-Open No. H08-184988. Further, a method of controlling a charge attenuation constant by forming the surface layer made of the thermosetting resin such as the melamine resin in the toner has been suggested in Japanese Patent Application Laid-Open No. 2015-219388. However, these toner particles do not have a condensate of an organosilicon compound, development durability or chargeability may be low. Further, performance to suppress over-charging may be insufficient as compared to that to be required.
As described in Japanese Patent Application Laid-Open No. H08-292599, the toner in which a surface of the toner to which an inorganic particle is fixed is coated with a silane coupling agent has also been investigated, but this toner may also have insufficient development durability and chargeability, and be overcharged in a low temperature and low humidity environment.
As described above, a toner having excellent development durability, high chargeability, and excellent overcharge suppression performance under a low temperature and low humidity environment has not been obtained, such that the toner should be improved.
The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide a toner having excellent development durability, high chargeability, and excellent overcharge suppression performance under a low temperature and low humidity environment.